Axillary infrared thermometer and cover therefor

ABSTRACT

An infrared detector has a probe having curved surfaces which slide readily into a neonate axilla. The probe is covered by a disposable cover, or a bag completely encloses the infrared detector. The bag has a pleated end surface, through which the detector views the skin, and a flap at a rear surface to close an opening which receives the detector.

RELATED APPLICATIONS

[0001] This application is a divisional application of U.S. Ser. No.09/290,286, filed Apr. 13, 1999, which is a divisional application ofU.S. Ser. No. 08/469,484, filed Jun. 6, 1995, the entire teachings ofwhich are incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002] Neonates are incapable of maintaining their own body temperatureduring the first few weeks of life. Skin perfusion rates are very highand the infant loses heat rapidly. Thermal management is critical,requiring an accurate, fast, noninvasive method of core temperaturemeasurement.

[0003] Rectal temperature has long been considered to be the standardindicator of neonate core temperature. However, since temperaturemeasurements from different locations on a neonate's skin aresufficiently uniform as to be relatively interchangeable with oneanother, the clinician may select the most noninvasive and convenientsite at which to measure temperature. Due to its inherent safety andlong established efficacy, axilla is the most recommended site forneonates. Unfortunately, conventional thermometers such asglass/mercury, electronic and paper strip thermometers require up toseveral minutes to obtain an accurate axillary reading.

[0004] In recent years, infrared thermometers have come into wide usefor detection of temperature of adults. For core temperature readings,infrared thermometers which are adapted to be inserted into thepatient's ear have been extremely successful.

[0005] Infrared thermometry has not found such high acceptance for usewith neonates. Neonates have a very high moisture level in their earcanals, due to the presence of vemix and residual amniotic fluid,resulting in low tympanic temperatures because of the associativeevaporative cooling. In addition, environmental uncertainties, such asradiant heaters and warming pads can significantly influence the airtemperatures. Further, clinicians are less inclined to position the tipof an infrared thermometer in the ear of a small neonate.

SUMMARY OF THE INVENTION

[0006] The present invention relates to an infrared thermometer which isdesigned for axillary temperature measurements. An infrared detectorprobe is designed to easily slide into the axilla to lightly touch theapex of the axilla. Because it relies on infrared temperature detection,a temperature reading can be obtained in as little as one-half second. Anovel cover is also provided to provide for ease of use in a sterileenvironment.

[0007] In accordance with the present invention, a person's temperatureis obtained using an infrared detector having a window through which asensor views a surface target. A sheet is stretched at least over aportion of the infrared detector, and a tip of the detector is pressedagainst the person's skin, with the sheet therebetween, to detect heatflux from the skin. Preferably, the window through which the sensorviews a surface target is at the base of a reflective cup.

[0008] In a preferred embodiment of the invention, the sheet is a bagwhich fully covers the infrared detector. The preferred bag isrectangular and open along an edge thereof. A flap at the open edge maybe folded over the opening to close the bag about the detector. The baghas a pleat, along an edge opposite to the open edge, which expands toprovide depth to the bag. The bag membrane is less than 1.25 milli-inchthick and preferably less than 1.0 milli-inch. The bag is preferablyabout 4 inches by 7½ inches with a pleat at least ½ inch deep,preferably about ¼ inch.

[0009] It is preferred that the sheet which covers the detector isinfrared transparent. However, the sheet may be opaque if it is able toquickly equalize in temperature with the target temperature. Thermalequalization is obtained quickly with a thin membrane. Thus, thoughthicker membranes may be used, it is preferred that the plastic membranebe less than 1.25 milli-inch to allow for prompt temperatureequalization. That temperature equalization is even important with atransparent membrane since the detector may still see heat flux from themembrane. With a transparent membrane, it is important that the membranebe kept thin in order to absorb as little infrared radiation as possiblepassing from the target to the detector and to assure prompt temperatureequalization of the membrane with the target.

[0010] The preferred detector comprises a main body to be held by handand a sensor probe. The probe has a first portion extending from an endsurface of the main body and a second portion extending from the firstportion substantially parallel to the end surface. The top of the secondportion and the outer corner where the first and second portions joinare rounded. The second portion of the probe has a frustoconical tipwhich ends at a cup in which the window is positioned. A peripheral beadsurrounds the probe behind the frustoconical tip to stretch thetransparent bag across the end of the tip. A nub extends from an endsurface of the main body opposite to the sensor probe, the nubstretching and retaining the transparent bag.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The foregoing and other objects, features and advantages of theinvention will be apparent from the following more particulardescription of preferred embodiments of the invention, as illustrated inthe accompanying drawings in which like reference characters refer tothe same parts throughout the different views. The drawings are notnecessarily to scale, emphasis instead being placed upon illustratingthe principles of the invention.

[0012]FIG. 1 illustrates one embodiment of a detector suited foraxillary temperature detection.

[0013]FIG. 2 is a side view of the probe of the detector of FIG. 1having a disposable cover positioned thereon.

[0014]FIG. 3 illustrates use of the infrared thermometer of FIG. 1 withthe cover of FIG. 2.

[0015]FIG. 4 illustrates an alternative embodiment of the infrareddetector.

[0016]FIG. 5 illustrates positioning of the detector of FIG. 4 in adisposable bag cover.

[0017]FIG. 6 illustrates use of the infrared thermometer of FIG. 5 inobtaining an axillary temperature measurement.

[0018]FIG. 7 is a side view of the infrared detector of FIG. 4.

[0019]FIG. 8 is a front view of the detector of FIG. 7.

[0020]FIG. 9 is a rear view of the detector of FIG. 7.

[0021]FIG. 10 is a top view of the detector of FIG. 7 with the tip ofthe probe shown in longitudinal section.

[0022]FIG. 11 is a bottom view of the detector of FIG. 7.

[0023]FIG. 12 is a perspective view of a bag cover prior to use.

[0024]FIG. 13 illustrates the bag of FIG. 12 expanded to illustrateopening of the pleated edge prior to insertion of the infrared detector.

[0025]FIG. 14 is a side view of the bag of FIG. 12.

[0026]FIG. 15 is a cross-sectional view of the bag of FIGS. 12 and 14taken along line 15-15 of FIG. 14.

[0027]FIG. 16 is a side view of the bag positioned over the infrareddetector.

[0028]FIG. 17 is a front view of the bag positioned over the infrareddetector as viewed along lines 17-17 in FIG. 16.

[0029]FIG. 18 is a top view of the bag positioned on the infrareddetector as in FIG. 16.

[0030]FIG. 19 is a bottom view of the bag positioned on an infrareddetector as in FIG. 16.

[0031]FIG. 20 is a bottom view as illustrated in FIG. 19 but with thelower nub removed to illustrate the possible failure of the bag withoutthe nub.

[0032]FIGS. 21A and 21B are front and side views of the detector probewith a bag cover which is not pleated.

[0033]FIGS. 22A, 22B and 22C are respective front, top and bottom viewsof the probe with a bag having a pleat with a less than optimal depth.

DETAILED DESCRIPTION OF THE INVENTION

[0034] The preferred embodiments of the present invention illustrated inFIGS. 1-6 are based on infrared temperature detection technologypreviously presented in U.S. Pat. No. 4,636,091; 4,993,419; 5,199,436;5,271,407 and 5,325,863, all assigned to Exergen Corporation. As inthose prior patents, an infrared sensor is positioned in a probe 30 or32 to view a target surface through a rigid window 34 or 36 at the tipof the probe. Four of the patents disclose infrared thermometersdesigned specifically for use as ear temperature detectors. Structuralmodifications of the probe for axillary temperature measurements includethe shape of the probe and the positioning of the windows 34 and 36 atthe bases of reflective cups 38 and 40. As described in U.S. Pat. No.4,636,091, the reflective cups are preferably conical. By positioningthe rim 35, 37 of a reflective cup against a surface, the target surfaceis viewed by the infrared sensor as a black body, so the cup providesemissivity compensation.

[0035] The embodiment of FIGS. 1-3 relies on a disposable probe coverpreviously presented in U.S. Pat. No. 4,993,419. The cover is a flatsheet having holes at opposite ends thereof. To position the cover overthe probe, one hole is positioned over a knob 42, the sheet is stretchedover the cup 38 at the tip of the probe and the other hole is thenpassed over the knob 42 to firmly retain the sheet over the probe. Thusstretched over the probe, the sheet follows the cylindrical surface ofthe end of the probe. The large curved surfaces, both around the endportion 44 of the probe and at its intersection with the base portion atthe corner 46, enable the probe to be easily slid into the axilla.

[0036] For improved cleanliness of the detector in the neonatologyenvironment, the embodiment of FIGS. 4 through 6 is provided. In thisembodiment, the entire detector, including the main housing 48 and theprobe 32, is inserted into a transparent bag 50 through a rear opening52. As described in detail below, the bag has a pleated front edge 54and a flap for covering the opening 52. In order to assure that theplastic bag stretches flat over the cup 40, the probe 32 is positionedsuch that the front portion 56 of the probe extends generally parallelto the end surface 58 of the main body of the detector. There is acurved surface across the top of the end portion 60 of the probe 32 anda rounded corner 62 to assure that the probe can be slid easily into theaxilla for use as illustrated in FIG. 6.

[0037] A side view of the detector embodiment of FIG. 4 is presented inFIG. 7. The main body 48 of the detector housing has a button 64 totrigger a temperature reading. Using the technology presented in theabove noted patents, the heat flux sensed by a sensor 65 is converted toa temperature readout on the display 66 at the bottom of the detectorhousing 48 (FIG. 11). That readout is obtained within approximately ½second.

[0038] A base portion 70 of the probe 32 extends normally from the topsurface 68 of the main housing 48 and then bends into a second portion72 which extends substantially parallel to the end surface 68. A ridge74 wraps about the base of the probe 32. The ridge 74 serves thefunction of preventing the button 64 from being activated when theinstrument is placed on a flat surface such as a counter top. It has acurved radius to avoid any sharp edges against the sensitive skin of theneonate. The tip of the probe at 76 extending to the cup 40 isfrustoconical, and a bead 78, having a soft radius, encircles the probejust behind the frustoconical tip. A nub 80 protrudes from the bottomsurface of the main housing 48 to facilitate positioning and retentionof the disposable cover as will be described below.

[0039] The use of the emissivity compensation cup facilitates accuratetemperature readings regardless of skin color and texture. Additionally,the transparent plastic membrane stretched across the cup eliminates aproblem presented by moist skin, that is, that evaporating moisturelowers the surface temperature of the underlying skin and presents alayer of cool vapor. By viewing the skin through the transparentmembrane pressed against the skin, evaporation is stopped, and the coolvapor layer is eliminated. Instead, a thin layer of liquid pressedbetween the transparent membrane and the skin equilibrates to the skintemperature.

[0040] As illustrated in FIG. 10, where the tip of the probe is shown inlongitudinal section, the metal cup 40 is surrounded by plastic material76 which extends slightly beyond the metal of the cup. As such, thepotentially cool surface of the metal does not touch the neonate's skin.This not only prevents discomfort to the neonate but also minimizescooling of the skin which might result in a reduced temperature reading.The field of view of the sensor is sufficiently narrow that it does notview either the cup or the surrounding plastic rim of the tip 76.

[0041] The disposable bag cover is illustrated in detail in FIGS. 12through 15. The bag is preferably formed of polyethylene membrane and isfabricated using conventional bag-forming techniques. However, the bagis dimensioned to meet this particular application and is formed of verythin plastic membrane to minimize absorption of the infrared radiation.The preferred membrane thickness is 0.8 mils. More generally, thethickness should be less than 1.25 mil and more preferably less than 1.0mil. The thinner membrane also softens the corner folds formed when thebag is stretched over an infrared detector as described below.

[0042] For a detector having a height of about 7¼ inches from the bead78 to the nub 80, and a width of about 3⅜ inches and thickness of about¾ inch, the bag is 7⅝ inches long and four inches wide. The flap ispreferably 1¼ inch wide. Those dimensions provide sufficient stretchingof the plastic membrane as the detector is inserted.

[0043] As illustrated in FIG. 15, where the thickness of the membrane isgreatly exaggerated, the bag is formed of a single sheet of materialwhich extends along one face 82 folds into a pleat 84, returns along aface 86, and is folded back at a flap 88. The bag is then heat sealed atthe top and bottom edges 90 and 92.

[0044]FIG. 13 illustrates the bag of FIG. 12 with the faces 82 and 86spread apart to open the pleat 84. The bag is not yet stretched over thedetector. The two walls 94 and 96 of the pleat are sealed to each otherand to the faces 82 and 86 along the edges 90 and 92. It can be seen inFIG. 13 that the edge 98 of the pleat remains fixed at point B behindthe end corner A of the edge even as the main length of the edge 98moves forward with expansion of the pleat. As a result, as the pleatexpands, the upper and lower corners of the bag distort such that thepoint A pulls up and to the rear and such that ears are formed at 100.The bag is designed in order to minimize the protrusions formed at pointA and ears 100 and to assure that they are pulled back away from the cup40. As such, any potential irritation to the neonate is minimized and aflat clear face of the plastic membrane is stretched over the cup forunobstructed infrared viewing.

[0045] To that end, the depth of the pleat along each of the surfaces 94and 96 is greater than the diameter of the tip of the probe which ispreferably about 2 inch. In particular, the preferred pleat depth isabout ⅝ inch.

[0046] The bag pulled fully over the infrared detector is illustrated inFIGS. 16 through 19. To position the detector in the bag, the probe isfirst inserted through the rear opening and the curved corner 62 of theprobe is appropriately pressed against the mid region of the bag asillustrated in FIG. 5. The housing 48 is then pivoted into the bag,stretching the bag over the nub 80. In the final position illustrated inFIGS. 16 through 19, the points B at the upper and lower edges of thebag are retained behind the bead 78 and nub 80, respectively. As such,the bag is prevented from slipping forward and it is retained stretchedover the front of the cup 40. The soft radiuses of the bead 78 and nub80 also prevent tearing of the bag at the seam as it is stretched overthe detector.

[0047] The nub 80 only extends along a length which is about half thethickness of the detector and is centered in the bottom surface. As thedetector is forced into position, stretching the bag, the mainstretching force is applied at the rounded corner 62 of the probe and atthe nub 80. Without the nub, it was determined that the bag wassusceptible to failure along the seam as illustrated in FIG. 20. Withoutthe nub, the bag was necessarily stretched across the outer edges of thebottom surface which tended to pull the seam apart, resulting in a holeat 110.

[0048] The importance of the pleat is illustrated by the comparison toFIGS. 21A and 21B. Without the pleat, a sharp corner protrudes in frontof the probe and may be a source of irritation to the neonate. Further,the two surfaces 82 and 86 do not stretch readily across the face of thecup and can result in some distortion along the fold line. With thepleat and sufficient stretching of the membrane, the side surfaces 82and 86 are pulled completely away from the end of the cup and the pleatsurfaces 94 and 96 readily form a flat transverse surface across thecup. Further, the potential corners at point A and at the ears 100 pullback snugly against the frustoconical tip.

[0049] Proper dimensioning of the pleat is also important as illustratedin FIGS. 22A through 22C. In this illustration, the pleat is of a depthbetween points A and B which is less than the diameter of the cup 40. Asa result, the point B does not reach behind the bead 78 and the bag isinclined to slip forward. Further, the bag tends to form larger ears 116which can irritate the neonate.

[0050] While this invention has been particularly shown and describedwith references to preferred embodiments thereof, it will be understoodby those skilled in the art that various changes in form and details maybe made therein without departing from the spirit and scope of theinvention as defined by the appended claims.

What is claimed is:
 1. An infrared thermometer comprising: an infrareddetector including an infrared sensor for viewing a target through awindow in a detector housing; and a removable bag enclosing thedetector.
 2. An infrared thermometer as claimed in claim 1 wherein thewindow is at the base of a reflective cup and the bag is stretchedacross the cup.
 3. An infrared thermometer as claimed in claim 2 whereinthe bag is rectangular and open along an edge thereof, the bag furthercomprising a flap at the open edge to be folded over the opening toclose the bag.
 4. An infrared thermometer as claimed in claim 3 whereinthe bag has a pleat along an edge opposite to the open edge, the pleatexpanding to provide depth to the bag.
 5. An infrared thermometer asclaimed in claim 4 wherein the detector housing comprises a main body tobe held by hand and a sensor probe, the sensor probe having a firstportion extending from an end surface of the main body and having asecond portion extending from the first portion substantially parallelto the end surface.
 6. An infrared thermometer as claimed in claim 5wherein the second portion of the probe has a frustoconical tip in whichthe window is positioned and a peripheral bead surrounds the probebehind the frustoconical tip to stretch the transparent bag across theend of the tip.
 7. An infrared thermometer as claimed in claim 6 furthercomprising a nub extending from an end surface of the main body oppositeto the sensor probe, the nub stretching and retaining the bag.
 8. Aninfrared thermometer as claimed in claim 1 wherein the bag isrectangular and open along an edge thereof, the bag further comprising aflap at the open edge to be folded over the opening to close the bag. 9.An infrared thermometer as claimed in claim 8 wherein the rectangularbag is significantly longer along its open length than it is wide. 10.An infrared thermometer as claimed in claim 8 wherein the bag has apleat along an edge opposite to the open edge, the pleat expanding toprovide depth to the bag.
 11. An infrared thermometer as claimed inclaim 10 wherein the bag is formed of infrared transparent plasticmembrane having a thickness of less than 1.25 milli-inch.
 12. Aninfrared thermometer as claimed in claim 1 wherein the bag has a pleatalong an edge opposite to the open edge, the pleat expanding to providethickness to the bag.
 13. An infrared thermometer as claimed in claim 12wherein the pleat has a depth of greater than ½ inch.
 14. An infraredthermometer as claimed in claim 1 wherein the transparent bag is formedof plastic membrane having a thickness of less than 1.25 milli-inch. 15.An infrared thermometer as claimed in claim 1 wherein the bag is formedof transparent plastic membrane.
 16. An infrared thermometer as claimedin claim 15 wherein the transparent bag is formed of plastic membranehaving a thickness of less than 1.25 milli-inch.
 17. A cover forcovering an infrared thermometer comprising: a rectangular bag formed ofplastic membrane of thickness less than 1.25 milli-inch, the bag havinga pleat along one edge thereof and an opening for receiving the infraredthermometer in a second edge opposite to the one edge, the bag having aflap at the second edge to be folded over the opening to close the bag.18. A cover as claimed in claim 23 wherein the plastic membrane has athickness of less than 1.0 milli-inch.
 19. A cover as claimed in claim23 wherein the pleat has a depth of greater than ½ inch.
 20. A cover asclaimed in claim 25 wherein the pleat has a depth of about ¾ inch.
 21. Acover as claimed in claim 23 wherein the bag has a length along thepleat and opening of about 7½ inches and a width of about 4 inches. 22.A cover as claimed in claim 27 wherein the length is about 7⅝ inches.23. A cover as claimed in claim 27 wherein the pleat has a depth ofgreater than ½ inch.
 24. A cover as claimed in claim 29 wherein thepleat has a depth of about ¾ inch.
 25. A cover as claimed in claim 23wherein the plastic membrane is infrared transparent.